Electrical Schematics (Industrial Controls)

Welcome to this lecture on basics of reading and understanding schematic.

Here we will study

• What is schematic ?

• How is it represented ?

• We will study about the template so that we will be able read and understand details about any given schematic.

We will be studying about the details that can be found in a template, about the schematic.

So go ahead, and get started!!

Parts of Templates.

Revision and Remark

Lets continue our learning, and let us further understand more details about schematics.

We will learn :

• What are schematics composed of ?

• On what basis is a schematic is drawn?

And before, we go any deeper into learning to read, understand and design schematics, we will learn

• Where are these schematics used ?

• Why are they needed?

Welcome back now that we have a basic understanding of

• What schematics are ?

• What are they composed of ?

• How are they represented?

• Where are they used?

• Why are they needed?

We will now move on the most basic building block of schematic - "The Symbols". Here we will cover the following symbols:

1. Wires - Connected & overlapping wires

2. Motor

3. 3-Phase supply

Note there are some of the very basic and most frequently used symbols while designing a schematic.

Connected wire Symbols

Here we will be studying about the most frequently symbols that help in building logic in the circuit : NO & NC contacts & coil

Then we will move on to symbols of switching devices such as

• Isolator

• Circuit breaker

• Emergency switches

• Contactor

• Transfer switches

• Selector switches, Ammeter & Voltmeter selector switch

• Limit switch

• Toggle switch

Symbols, Contacts

In this lecture we will be studying about the symbols of Push buttons and Indicators.

We will also learn about the difference between momentary and latching action function.

In this lecture we will be studying about the symbols of Instrument transformers and various types of meters.

• Current Transformers (CT's) & Potential Transformers (PT's)

• Ammeter

• Voltmeter

• kWh meter

• Frequency meter etc.

Transformer Symbol

In this lecture we will be studying about the symbols of various types of protection devices used in the circuits such as

• Fuse

• Over voltage relay

• Under voltage relay

• Thermal overload relay

• Timer

• Thermostat

• Terminals etc.

Relay Symbol

Quick Recap of the topics cover in section 1.

1. Basic of Schematics

2. Template

3. Symbols - Switching devices , meters , indicators protective devices etc.

Terminal Symbol

Welcome to Section 2 of Electrical Schematic course.

We will first understand what is on load and off load application.

Then later in this section we will learn more about certain key components to understand where, and why, symbols of these components must be placed in a schematic.

We will cover the following switchgears:

1. Switch – Isolators

2. Circuit Breakers

3. Contractor and contacts

4. Lamps and Push buttons

5. Meters and Protection devices

On load device.

In this lecture, we begin with our study on the first switchgear i.e. Isolators

We will learn

• what is an isolator ?

• Understand where Isolators can be used.

Keeping our understanding of the lesson learnt in section 2.1, we will learn whether the Isolator is an ON load device or an OFF load device. So, lets us being our learning.

Isolator

In the previous lecture we learnt about the Isolator. We will now learn about Circuit Breakers.

We will learn the definition of circuit breaker and its review its symbol. Then we will understand the difference between and Isolator and circuit breaker.

We will also see the different types of circuit breakers based on their application

• VCB

• SF6

• ACB

• MCCB

• MCB.

Circuit Breaker and Isolator

We will learn about contactor and contacts. This one of the key switchgears used to develop logic and control in the circuit.

We will learn about

• Power contactor

• Auxiliary contactor

• Contact numbering

• Application of contactor

• Limitation of contactor

Aux. contactor

In this lecture we will learn more about Indicators. Then we will move on to meters and finally learn why instrument transformers are need to used with meter & certain protective devices.

Switchgear Details: Indicators, Metering & Instrument Transformers

In this lecture we will learn more on protection devices and learn that certain protection devices are directly connected in the power circuit whereas others are connected using instrument transformer.

Thermal overload relay.

Welcome to this section on designing of schematics. In this section we will learn to develop simple circuits. While learning to develop circuits we will come across various concepts used to design schematics. But before we can start designing schematics there certain basic concepts about the schematic that we should be aware of.

In this lecture we will learn about the Basics of power and control circuit. We will learn

• What is power circuit ?

• What is a control circuit?

• What is the difference between them ?

So, lets begin our learning.

Power and Control Circuit

Welcome to this lecture on Power Circuit.

Here we will learn to design simple power circuits. We will use all the basic concepts that we have learnt till now to start designing schematics.

We will go in step by step method. Hence, we will be first defining the requirement and then start designing it.

Therefore, we recommend you to keep a pen and paper handy with you from now on. You may pause the lecture in between and try designing the circuit based on the requirement. This will help you learn & understand faster.

In this lecture we will get a basic understanding of the Direct on line starters and what are the other types of motor starter circuits that are used for starting a motor.

DOL circuit

Welcome to this lecture on DOL circuits. In this lecture we will learn:

1. How to design a basic DOL Circuit?

2. And why are motor starters required during starting of a motor?

Overload Protection & Switching Device

Overload Protection

Hold-on Contact

Stop Push Button

Reading & understanding Schematics 

Legends

Control Circuit

Local and Remote Operation

Remote Indication

Welcome to this section of basics of interlocking. Here we will be covering

• What does interlocking mean

• Type of interlocks

Application of reversible motor.

In this lecture, we will understand and develop an electrical interlocking circuit in a step by step method.

Electrical Interlocking

Welcome to this section on Metering circuits.

In this lecture we will be covering basics of meters and understand how voltmeter and ammeter can be connected in a circuit.

Ammeter

Here we will use the lesson learnt in the previous lecture and develop basic metering circuit.

Calculate current

In the lecture, we will understand where schematics find extensive application.

Schematics in Switchboards

Welcome to the last lecture, we will sum up all the concepts that we have covered throughout this course and we will also share what is the next step to do after completing this lecture.